The present invention relates to an instrument for implanting delicate tissue and/or materials in the human body, more particularly to an instrument for surgically restoring eyesight by implanting fetal retinal tissue into the subretinal space in the back of the eye.
Most common eye problems, for example, myopia (nearsightedness), hyperopia (farsightedness), astigmatism (asymmetrical cornea, and presbyopia (the inability to focus on an object at close range) are due to errors in the refraction of light by the lens and cornea in the anterior part of the eye. Generally, these problems can be corrected by glasses, contact lenses, or corrective surgery.
However, blindness is most commonly due to damage of the retina in the back of the eye and, more specifically, is caused by abnormalities in the subretinal space under the retina.
The transparent, layered retina processes light images projected by the cornea and lens. The photoreceptor layer in the back of the retina transforms the light into electrical impulses. Other retinal layers transfer these impulses through the optic nerve to the brain which interprets the impulses into what we perceive as sight.
The subretinal space is the area between the retinal pigment epithelium (RPE) and the photoreceptors of the retina. Normally, the photoreceptors are in close contact with the RPE. The RPE has many functions. It provides nutrition for the photoreceptors, and also removes waste products from the photoreceptors. In a normal eye, there are no blood vessels in the subretinal space. However, in some retinal diseases, blood vessels and connective tissue can grow in this space and cause blindness. Under certain disease conditions, the photoreceptors can be detached very easily from the RPE. The photoreceptors will then degenerate, resulting in vision loss or blindness, while the other layers of the retina may remain functional. By replacing the diseased RPE and/or photoreceptors that can hook up to the functional part of the retina, vision may be restored.
The most frequent cause of legal blindness is macular degeneration and retinitis pigmentosa. The macula is located in the back of the eye in the central portion of the retina and is responsible for central vision. In patients with macular degeneration, there is initially a dysfunction of the RPE in the macular region, which later leads to ingrowth of blood vessels and destruction of the light-sensitive photoreceptors in the overlying retina. This results in impairment of central vision. Age related macular degeneration is an example of an eye disease that can be delayed by using the herein disclosed method and instrument.
Retinitis pigmentosa is a term for genetically caused photoreceptor degeneration. In these patients, the photoreceptors must be replaced. Again, the method and instrument of the present invention can be utilized.
It is to be noted that surgical correction of diseases in the subretinal space between the retina and the RPE is rendered extremely difficult by the environment in which the surgery must take place. Moreover, the surgical procedure disclosed herein to implant fetal retinal tissue into the subretinal space of the eye is complicated by the fact that fetal retinal tissue is in the nature of a transparent gelatinous mass and therefore extremely fragile.